The chemical structures of some common polycyclic aromatic hydrocarbons are shown in FIG. 1. Polycyclic aromatic hydrocarbons (PAHs) may be formed when organic materials are heated and are sometimes found in materials that are intended for human consumption such as smoked food, fried food or tobacco products. Since many polycyclic aromatic hydrocarbons are known or suspected to be carcinogenic, it can be desirable to remove them from such materials. Benzo[a]pyrene is a typical polycyclic aromatic hydrocarbon and is known to be carcinogenic.
In some processes for removing polycyclic aromatic hydrocarbons, the polycyclic aromatic hydrocarbons first need to be extracted from a material in which they are present using an extraction medium and thereafter removed from the extraction medium. The extraction medium may extract other constituents of the material, and it may be desired to return these other constituents to the material and to remove the extraction medium, so that losses of the other extracted constituents are minimized. In such processes, it is required that polycyclic aromatic hydrocarbons be selectively removed from the extraction medium, e.g. with a selective adsorbent.
There are also situations where polycyclic aromatic hydrocarbons are dissolved in liquids and need to be removed therefrom. For example it may be desired to remove polycyclic aromatic hydrocarbons from contaminated vegetable or animal oils or essential oils.
In other situation, the purpose of the extraction may be analytical, in order to quantify the levels of polycyclic aromatic hydrocarbons in a material. In some analytical methods, the polycyclic aromatic hydrocarbons are first extracted from the material using an extraction medium and then adsorbed to an adsorbent. The polycyclic aromatic hydrocarbons can then be released from the adsorbent with an elution solvent and quantified. Sometimes, one or more washing steps are employed before the polycyclic aromatic hydrocarbons are released to selectively release other bound compounds. In such methods, it is desirable that the adsorbent is selective in order to eliminate other constituents that may distort or disturb the analysis.
Molecularly imprinted polymers (MIPs) are a class of selective adsorbents. Molecularly imprinted polymers are polymers that are prepared in the presence of a template molecule leading to the formation of sites that are complementary to the template and can selectively bind the template and other functionally related molecules. However, hitherto, MIPs have not performed well in the extraction of polycyclic aromatic hydrocarbons.